MRP Generated Purchase Requisitions

All,
Here is my dilemma. Customer wants MRP to generate Purchase Requisitions based on a demand element like normal. Multiple issues occur and will do my best to explain.
Data:
Truckload of 40,000 LB
When any demand >= 1 LB the customer would like 4 purchase requisitions of 10,000 LB a piece. The reasoning is that each purchase requisitions equals one truck load and they want 4 truck loads in no matter how much demand they have.
They do not want 1 requisition of 40,000 LB
Material is PD planned (obviously)
If total demand is over 40,000 LB, they do not want another truck load for the month.
4 requisitions a month total which = total of 40,00 LB
PDT is 90 days with GR processing time of 5 days.

Any help would be appreciated if this can be solved by standard MRP ways.

Perhaps, my proposed solution might not be workable but have you thought of using the rounding profile where SAP will generate one PR for the "round-up" quantity of 40,000 LB if the demand quantity is from 1 to 40,000 LB?. Seconldy, why would you like to generate 4 separate PRs?

Our customer wants four seperate Purchase Requisitions because each requisition represents a truck load and they want a one to one relationship of requisition to purchase order. I suggested manually making four purchase orders from one requisition but they think it is too manual and want MRP to generate four seperate requirements.

Unfortunately, standard SAP does not generate four separate PRs for the same demand requirement. BTW, why would your customer like to generate four PRs for four trucks as you can well manage it via LE process instead of purchasing process.

Is this vendor on auto PO generation? If not I do not see an issue as the buyer must convert PR to PO and can control this function unless Purch mgr. does not trust buyers to do their job. If vendor is on auto PO, then the vendor could control the delivery if timing of delivery is the issue. Or is accts payable the real issue about possibly paying for a delivery once a week instead of 4 at a time (money flow)? I think you need to dig deeper and find the REAL driver behind your dilemna.

Before you go customizing, please try lot size fixed and splitting. your lot size is 40000 with a rounding value of 10000, leave the takt time blank, and with any demand greater than one you should get 4 reqs for 10,000 each. since takt time is blank, datewise should be the same date. demand for 40001 will create 8 reqs.

Actually there is no standard MRP solution for what you are trying to accomplish. MRP will always create supply for uncovered demand & net to zero. So if 40,001 LB are ordered then MRP will create supply to cover the 40,001 LB regardless of the MRP settings being used.
The best available standard MRP solution for this is to use a Lot Size Strategy of "FS" for Fixed & Splitting. The Fixed Lot Size needs to be set to 40,000 & the Rounding Value set to 10,000. MRP will generate a supply of 40,000 that will be split into 4 separate purchase requisitions for 10,000 each. Unfortunately, if the demand is 40,001 LB then MRP will create 4 purchase requisitions for 10,000 each to cover the 40,000 LB & create 4 purchase requisitions for 10,000 each to cover the 1 LB. The result is an over-coverage of 39,999 LB. Purchasing would have to manually control the 40,000 per month limit.

So, long as you are using mrp type PD you are correct, demand will drive to cover shortages. you can modify time and quantity but planned inventory below zero will always launch new orders.
If you want to exclude demand, you could try one of the consumption based mrp types. VB manual reporder point. then demand will not drive mrp planning, only when your combined inventory and PO's fall below your designated reorder point will you get requirements. Take some effort to select the proper re-order point. It sounds like you need to launch your orders 90 days in advance for lead time. Quickly if you consume 10m per week, and you lead time is 90 days, you should set your rop to 90000, and again keep your FS lot size. 40000 and rounding 10000. I might put a takt time in of 7 days, then whenever you went below your rop SAP would generate 4 reqs in a row for delivery every 7 days (weekly) .
so lot size drives total of the reqs, rounding value drives individual qty of reqs. and takt time can modify the timing of the reqs.
The only other option for time phased delivery is time phased mrp types.. they require integration of the forecast (historical consumption) I have looked at them, but never used them. SAP insider has an excellent book on the "inventory optimization with SAP". If covers alot of the reasons, rules, and outcomes for selecting different mrp types, planning strategies, and lot size strategies.. There are lots of functions in standard SAP that I would look at and consider before I thought about ABAP customizing..

it looks like you want 40000 lbs to be the absolute maximum order qty. Is this due to storage constraints ? You could use a combination of fixed lot size and maximum stock level field. The maximum stock level field is I think on one of the MRP views. Dont have the system in front of me right now.

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